Document scanners convert a visible image on a document, photograph, a transparent media and the like into an electronic form suitable for copying, storing and processing by a computer. A document scanner may be a stand-alone device or integrated with a copier, a facsimile machine, a multipurpose device, etc.
Scanners have a transparent plate or platen against which an object to be scanned is placed. The document is scanned by sequentially imaging narrow strips, or scan line portions, of the document on a linear optical sensor array such as a charge-coupled device (CCD). The optical sensor array produces electronic data which is representative of each scan line portion of the document which is imaged thereon.
In one type of scanner, the platen and document remain stationary and at least a portion of an imaging assembly is moved to change the scan line portion which is currently imaged. Many scanners comprise a fluorescent lamp typically implemented as a tube having a phosphor coating around the inside surface thereof. Fluorescent lamps generate light by passing electricity through the lamp tube. The lamp tube holds an inert gas and typically a quantity of mercury. The electricity passing through the lamp tube energizes mercury atoms and energy in the form of light photons is emitted therefrom. The light emitted from the tube comprises a majority of ultraviolet (UV) photons with a small amount of visible light photons. Phosphors, or another fluorescent substance, is coated around the inner surface of the lamp tube and converts the invisible UV light into visible light.
Fluorescent materials that absorb light of one wavelength, e.g., invisible UV light, and that re-radiate light at another wavelength, e.g., a visible light wavelength, are said to fluoresce and appear to glow when exposed to black light in the absence of irradiation of light in the visible light spectrum. Fluorescent colored inks, dyes, and paints are used to create various “glow-in-the-dark” products that fluoresce when irradiated with UV light. For example, images may be printed on a document with fluorescent ink that are invisible when illuminated with visible light but that visibly fluoresce when irradiated with a black light.